I Promise
by A Sirius Crush On Moony
Summary: I promise to never let him know. He's my brother - I should not love him the way I do, but I can't help it. Regulus/Sirius incest


**I don't know. I wanted to write something Blackcest-y, and this just popped into my head. It will be a multi-chap, so if you like the first chapter, then you can expect more to come :)**

**Warnings - Incest (duh), if you don't like it then _don't read it. _**

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><p><span><strong>I Promise<strong>

_**To Never Let Him Know**_

Anger burns through me like Fiendfyre. He stands before me, that smirk carved into his face and that glimmer of excitement in his eyes. He holds up the simple pieces of parchment that are bound together so intricately, and waves them in the air as though they do not hold together every little thought, memory and feeling I have had since, well, for as long as I can remember. I want to lunge towards him and rip my diary from his hand but I know that he is stronger than I am. I have always been the weak one. Keeping my cool, I stand up straight, trying to feel the flames behind my eyes blow out.

"Give it back, Sirius."

I am surprised at how calm I sound when in reality I am full of panic. I watch his face as he hears my words and he just smiles an even more excruciating smile. He flicks through the pages, keeping his eyes on me. My heart is thumping loud in my chest and my throat has suddenly gone extremely dry. The way his fingers flick through the pages so carelessly and effortlessly, makes me sick that it can be _that_ easy to uncover somebody's deepest secrets. And of all the people to find my diary is _has_ to be the one person I fear the most from finding it.

I decide that diaries are ridiculous things. Why have I spent my entire life writing my everythings down into that book, when all it takes is for it to fall into the wrong hands for my world to break apart?

He opens the book and his eyes land on one of the pages. I run towards him, desperate now to wrench the book from him. His invasion of my privacy makes my anger bubble up more.

"Give me the book back, _now_!"

Sirius lifts the book high into the air. Too high, so that now I can't reach it. I grasp at the sleeves of his robes, a sheet of sweat now all over my body. I try to pull his arms down so that I can get the diary back, but he's strong.

"_Today he walked past me in the corridors,_" Sirius says in a mocking tone, smirking at me. "_I swear my heart nearly jumped out of my chest when he smiled at me. I rarely smiles at me. I just wanted to run towards him and..._" Sirius glances down at me, looking confused.

I shrink back against the wall, giving up. He's obviously read what I feared he would read. The way he's looking at me makes me want to throw up. Instead I just hug myself and stare at my feet pathetically.

"I didn't know you were gay, Reg," Sirius says. "You wanted to _kiss_ this guy you were going on about?"

My cheeks burn, and I realise he hasn't read the worst part yet. I lunge forwards, taking him by surprise, and I snatch the book out of his hands, probably with more force than needed.

"It's none of your business," I croak, holding my diary close to my chest. Sirius grins and I hate to think of what his plan may be.

"But you're my little brother," Sirius says, in a belittling tone. "Of course it's my business. _Accio._"

Before I realise what is happening, the diary is back in his hands. I plunge my hands into my robe pockets to find my wand, and to my horror, I have left it in the dorm.

"Please, Sirius."

Sirius rolls his eyes and opens the book again. "_I had my first sex dream about him last night_," Sirius glances up at me, and I am mortified. "Tut tut, Reg. Anyways, _it made me feel so embarrassed but also it was the best dream of my life._"

"Can you stop, please?" I plead, feeling physically sick. "You can't do this."

"Oh come on, how bad can it be?" Sirius asks me, and I can feel tears in my eyes because I know what's coming up next. I only wrote this two weeks ago.

"_I know it's wrong to love him this way, and I know it's wrong to have sex dreams about him because he's my brother, but- _WAIT, WHAT?" Sirius throws the diary to the floor as though it has burned his hands, and glares at me in a mixture of disbelief and disgust.

I want to reach for my diary, but I am rooted to the floor in fear. What will he do to me? Will he tell anyone? I can feel myself shaking. His words just echo over and over in his head, and the room seems to be spinning. I have never felt so frightened in my life before.

"_Riddikulus_!"

Suddenly, Sirius is gone and Professor McGonagall is standing before me, looking worried. I blink and instinctively look for my diary, which seems to have disappeared with Sirius. I glance back at Professor McGonagall and I can't help but burst into tears. I feel childish and weak doing so but the tears are like waterfalls, spilling over my bottom lid and running down my face.

"It's alright, Mr Black," Professor McGonagall says calmly, awkwardly placing her hand on my shoulder and squeezing it a little. "It was just a Boggart. It's gone now."

"A b-b-boggart?" I stutter, feeling a wave of relief rush all over me. I have never encountered one before, but I know all about them. I didn't know they could be so convincing till now.

"Yes, it's okay. I got rid of it."

I let out a loud sigh and wipe away my tears with my sleeve. "Thank you," I say, smiling a weak smile at the Professor. She smiles back warmly.

"Next time, remember to have your wand with you, won't you?"

"I promise," I say quickly.

And to myself I make a silent promise; _I promise to never let Sirius find out I am in love with him._

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